System and Method to Eliminate High Pressure Surges in HVAC Systems

ABSTRACT

A system and method are disclosed for relieving high pressure within an HVAC system. A bypass line is provided that can direct refrigerant away from a condenser within the HVAC system. The bypass line can direct the refrigerant toward an inlet to the evaporator within the HVAC system. Other locations of bypass lines can be used as well. A controller for the HVAC system can control access to the bypass line and measure pressure within the system. An orifice can be provided within the bypass line to help relieve pressure within the HVAC system.

TECHNICAL FIELD

The present disclosure is directed to HVAC systems and more particularly to pressure relief for these systems.

BACKGROUND OF THE INVENTION

HVAC systems may have pressure sensitivities during operation. For example, air conditioners may include microchannel condensers (e.g., condenser with a channel size less than approximately 1 mm) rather than other types of condensers (e.g., condenser with tube size greater than 5 mm). The buildup of refrigerant pressure in HVAC systems is a common problem. The problem can be particularly acute in systems with a microchannel condenser because microchannel condensers may be sensitive to certain operating conditions. For example, when ambient temperatures (e.g., temperatures proximate a condenser or temperature proximate a condenser fan) are high, the pressure in the microchannel condenser may become elevated due to the refrigerant capacity size difference between the microchannel condenser and the evaporator. The high pressures (e.g., pressures greater than approximately 615 psi, in some embodiments) may cause mechanical failure, including prefailure events, such as excessive wear on parts. High pressures may also trip safety systems designed to prevent overpressure. One previous solution has been to limit refrigerant within an HVAC system. However, this solution leads to a loss in efficiency.

A particular problem can occur upon startup of an HVAC system. Refrigerant may not be evenly/properly distributed within the system, leading to refrigerant and/or pressure imbalances. One solution has been to change the size of microchannels within the HVAC system, such as in the condenser. However, this may limit other properties or capabilities of the system, and such a solution may not be feasible as a retrofit solution.

BRIEF SUMMARY OF THE INVENTION

One embodiment of the present disclosure comprises an HVAC system comprising: an evaporator operable to receive refrigerant from a liquid line and evaporate a portion of the refrigerant into a gaseous state; a pressure sensor, the pressure sensor located within the liquid line and operable to measure the pressure within the liquid line; a compressor operable to receive refrigerant from the evaporator; a condenser operable to receive refrigerant from the compressor discharge line and condense a portion of the refrigerant into a liquid state; an expansion device operable to receive refrigerant from the condenser and direct the refrigerant toward the evaporator; a bypass line, the bypass line operable to direct refrigerant away from the condenser and return the refrigerant to the HVAC system, the bypass line comprising a valve and an orifice; and a controller, the controller coupled to at least the pressure sensor and the valve of the bypass line, the controller operable to open the valve when the pressure reaches a predetermined value.

Another embodiment comprises a method of operating an HVAC system comprising: receiving, at a controller, a signal to start the HVAC system; starting, by the controller, the HVAC system; receiving, at the controller, a pressure measurement within the HVAC system; sending, by the controller, a message to open a valve in a bypass line when the pressure measurement is above a predetermined threshold, thereby directing at least some refrigerant away from a condenser inlet and toward an evaporator inlet, wherein the bypass line comprises an orifice; and sending, by the controller, a message to close the valve when a predetermined event has occurred.

Another embodiment comprises a method of relieving pressure within an HVAC system comprising: starting the HVAC system; receiving a pressure notification when pressure within the HVAC system exceeds a predetermined threshold; opening a bypass line in response to the pressure notification, the bypass line capable of diverting at least some refrigerant away from a condenser inlet and toward an evaporator inlet, the bypass line comprising a valve and an orifice; and closing the bypass line when a predetermined event has occurred.

The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagram of a system embodiment of the present disclosure.

FIG. 2 is an alternate diagram of a system embodiment of the present disclosure.

FIG. 3 is an alternate diagram of a system embodiment of the present disclosure.

FIG. 4 is a chart of experimental data from the use of the present disclosure.

FIG. 5 is a flow-chart diagram of a method embodiment of the present disclosure.

FIG. 6 is an alternate flow-chart diagram of a method embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

HVAC systems may have pressure sensitivities during operation. For example, air conditioners may include microchannel condensers (e.g., condenser with a channel size less than approximately 1 mm) rather than other types of condensers (e.g., condenser with tube size greater than 5 mm). Microchannel condensers may be sensitive to certain operating conditions. For example, when ambient temperatures (e.g., temperatures proximate a condenser or temperature proximate a condenser fans) are high, the pressure in the microchannel condenser may become elevated due to the refrigerant capacity size difference between the microchannel condenser and the evaporator. The high pressures (e.g., pressures greater than approximately 615 psi, in some embodiments) may cause mechanical failure, including prefailure events, such as excessive wear on parts. High pressures may also trip safety systems designed to prevent overpressure. If air conditioner operation is allowed when the pressure exceeds a predetermined operational maximum (e.g., greater than approximately 615 psig and/or greater than approximately 620 psig for R410A, in some embodiments), mechanical failure events may occur. For example, mechanical failure events, including pre-failure events, may include wear on parts, damage to lines, damage to seals, and/or damage to components. Startup of HVAC systems can provide unique pressure problems as well. HVAC systems may have startup problems with microchannel condensers because of the refrigerant storage imbalance between a microchannel condenser and round tube flat fin coil evaporators. If the microchannel tube port size is too small, the HVAC system start up problem may be elevated. Various condenser and evaporator types and geometries can cause pressure spike or buildup problems.

In a typical prior art system, refrigerant passes through an evaporator, pulling heat from surrounding air, and evaporating the refrigerant to gas form. Then the gas can be compressed in a compressor before passing through a condenser. As gas refrigerant passes through a condenser it loses heat to the surrounding air, leaving the refrigerant again in liquid form. The refrigerant then flows through an expansion device to the evaporator. In some embodiments, the evaporator is located within a room or building, creating a cooling effect (an air conditioner). Other embodiments may place the condenser inside a room or building, creating a warming effect (a heat pump).

The present disclosure includes methods and systems to solve the stated problems. One embodiment, such as shown in FIG. 1, is to use a bypass line 58 with a shut off solenoid valve 55 to bypass an expansion device 50. The solenoid valve 55 can remain open when the unit is started and will be shut off within a few minutes after startup of the system. The exact time required to shut off the solenoid valve 55 may vary for different HVAC systems. The shut off solenoid valve 55 can be also controlled by the signal of compressor discharge pressure. For example, if the compressor discharge pressure is close to the high pressure switch setting pressure, the solenoid valve 55 will be open a short time as required to prevent high pressure switch tripping off. If the high pressure surge is still high enough to trip off the high pressure switch valve, a hot gas bypass 68 from the outlet of compressor 30 to the inlet of the evaporator 20 may be necessary. A pressure regulating valve 65 can be used in the hot gas bypass 68 so that the compressor discharge pressure cannot be reached to trip off the high pressure switch. Bypass line 68 can also comprise an orifice 67 to help relieve pressure. An alternative way for the hot gas bypass 68 is to use a solenoid valve to control the hot gas bypass 68. If the compressor discharge pressure reaches close to the high pressure switch trip off pressure, the solenoid valve in the hot gas bypass 68 will be open for a required short period of time to release the compressor discharge pressure.

FIG. 2 displays an alternative embodiment of the present disclosure. HVAC system 100 comprises an evaporator 120, compressor 130, condenser 140, expansion valve 150, valve 165, and distributor 170. A plurality of pressure sensors can be located at various locations within system 100, including at any of the numbered elements. A controller (not shown) may be connected (wired or wirelessly) with a plurality of pressure sensors and/or the other components. The controller can thereby monitor the pressure of the system and adjust valves and other components accordingly. As shown in FIG. 2, if there is a pressure spike, the valve 165 (possibly a solenoid valve and/or a pressure regulating valve, or another type of valve) may open, diverting at least some refrigerant into bypass line 168 from condenser 140 and expansion device 150 and relieving the system 100 from high pressure. Orifice 167 may also be open (it is preferably always open), allowing pressure to escape.

In some implementations, the condenser may be a microchannel condenser. A microchannel condenser may include channels less than approximately 1 mm. The channels of the microchannel condenser may have a cross-sectional area similar to a rectangle, an oval, and/or any other appropriate shape. A microchannel condenser may increase the efficiency and/or decrease energy consumption of an air conditioner (e.g., when compared to an air conditioner with a condenser with a tubing diameter greater than 5 mm). A microchannel condenser may be able to operate with less refrigerant (e.g., when compared to an air conditioner with a condenser with a tubing diameter greater than 5 mm).

In some implementations, a part of the refrigerant may flow through the bypass line (elements 68, 58, 168, 258, 268 from FIGS. 1, 2 and 3). For example, less than 50 percent of the refrigerant in a line (e.g., a line from the high pressure portion) may be allowed to flow through the bypass line. In some implementations, approximately 5 to approximately 10 percent of the refrigerant may be allowed to flow through the bypass line. Less than 20 percent of the refrigerant in a line may be diverted to flow through the bypass line in some implementations. In some implementations, the amount of refrigerant allowed to flow through the bypass line may be at least partially based on a size of the bypass line (e.g., absolute size and/or size of the bypass line compared to other lines in the air conditioning system). The size (e.g., diameter and/or cross-sectional area) of the bypass line may be selected to allow a predetermined amount of refrigerant to flow through the bypass line.

FIG. 3 shows an alternate embodiment with pressure sensors 256, 266 coupled to valves 255, 265 that may control the amount of refrigerant allowed to pass through the bypass line 258, 268. The valves 255, 265 may be disposed in the bypass line 258, 268. A sensor 256, 266 may be coupled to the valve 255, 265 and/or operations of the valves 255, 265 may be based at least partially on the property reading from the sensors 256, 266. For example, the valves 255, 265 may open when a property reading exceeds a predetermined maximum property. The valves 255, 265 may close at other times. For example, a valve 255, 265 may automatically close and restrict flow through the bypass lines 258, 268 when a property reading does not exceed a predetermined maximum property. In some implementations, the valves 255, 265 may automatically operate based on the property reading. Bypass line 268 may also comprise an orifice 267. During high pressure events orifice 267 (preferably maintained as a fixed opening) can help relieve pressure within the system. As shown in FIG. 3, orifice 267 will only be used when valve 265 is open and bypass line 268 is being utilized. FIG. 3 also shows a controller 280 coupled to the valves 255, 265, sensors 256, 266 and other elements of system 200. The controller 280 may control the openness of the valves 255, 265 to control the amount of refrigerant allowed to pass through the bypass lines 258, 268. The controller may include a computer and/or other programmable logic device. The controller may comprise an interface for use by a user. Alternatively a user interface may comprise a separate component in communication with the controller. Valve 255 and sensor 256 may be set for different pressure measurements (or other properties) than valve 265 and sensor 266, so the two bypass lines may function independently of one another. Controller 268 can also comprise a connection to orifice 267 (not shown).

The sensors 256, 266 may detect other properties of the air conditioning system 200. For example, the sensor 256, 266 may detect properties such as temperature, pressure, and/or other appropriate properties. The sensor 256, 266 may detect the property at various positions in lines and/or components of the air conditioning system. For example, the sensors 256, 266 may detect a property (e.g., temperature and/or pressure) such as an ambient temperature (e.g., a temperature proximate the condenser). The sensors 256, 266 may also be disposed at a plurality of other locations within system 200.

In keeping with the teachings of the present disclosure, a high pressure switch can be located at any suitable location within an HVAC system. For example, the high pressure switch may be disposed proximate an outlet of the compressor, and/or proximate an outlet of the condenser.

In some implementations, when the air conditioner includes a condenser that is not a microchannel condenser, high pressures (e.g., greater than predetermined maximum and/or predetermined operational maximum) may not occur (e.g., during high ambient temperature operations) due to the smaller capacity difference between the condenser and the evaporator (e.g., when compared to the capacity difference between a microchannel condenser and an evaporator). But the teachings of the present disclosure can still be used for non-microchannel implementations.

FIG. 4 shows the results of experiments using the teachings of the present disclosure. FIG. 4 shows a pressure spike event and several resulting pressure measurements before, during and after the event. For example, P_(dis) 310 (discharge pressure) and P_(Liquid) 320 (liquid pressure) are shown. Both pressures spike shortly before time 14:01:10, but are then relieved. The pressure spike reaches a maximum at the moment the bypass valve is opened. The pressure then lowers and the bottom point is the moment when the bypass valve is closed. After that point the pressure then plateaus at a manageable level. The time required to remove the severe system pressure can change depending on the specific geometry of each individual embodiment. Typically it will take 40 seconds to a minute and a half to relieve the system pressure. The suction pressures P_(suction) 330 is also shown. The x-axis 340 is time and the y-axis 350 is pressure.

FIG. 5 illustrates an implementation of an example process 400 for an operation of an air conditioning system. A signal is received to start an HVAC system 410. The HVAC system is started 420. A pressure measurement is received from within the HVAC system 430. A message is sent to open a valve in a bypass line when the pressure measurement is above a set value 440. A message is sent to close the valve when a predetermined event has occurred 450.

FIG. 6 illustrates another method embodiment 500 of the present disclosure. The HVAC system is started 510. A pressure notification is received when pressure within the HVAC system exceeds a set value 520. A bypass line is opened in response to the pressure notification 530. The bypass line is closed when a predetermined event has occurred 540.

If the pressure reading exceeds a predetermined maximum, flow through the bypass line may be allowed. For example, the controller may transmit a signal to a valve disposed in the bypass line. The valve may at least partially open if the property reading exceeds the predetermined maximum property. In some implementations, the amount of refrigerant allowed to flow through the bypass line may be based at least partially on the degree of openness of the valve. The amount of refrigerant allowed to flow through the bypass line may be based on the size of the bypass line. Allowing fluid flow through the bypass line may reduce a pressure of at least a part of the high pressure portion of the air conditioner. If the property reading does not exceed the predetermined maximum property, flow through the bypass line may be restricted. For example, a valve disposed in the bypass line may be closed if the property reading does not exceed the predetermined maximum property.

A determination may be made whether a pressure reading exceeds a predetermined maximum pressure reading. For example, a predetermined maximum pressure reading may be retrieved from a memory of the air conditioner and/or controller. The pressure reading and the predetermined reading may be compared (e.g., by a processor of the controller of the air conditioner, by a valve controller, and/or by the sensor). In some implementations, the pressure reading may be a pressure differential across the compressor and the predetermined maximum pressure differential across the compressor may be 460 psi for R410A. The pressure reading may be an absolute pressure and the predetermined maximum pressure may be 600 psig. For example, a pressure of refrigerant in a line may be a measured pressure reading and the associated predetermined maximum pressure reading may be 600 psig. In some implementations, the predetermined maximum pressure may be a preselected amount (e.g., 10 psi, 15 psi, and/or 20 psi) less than the maximum operational pressure (e.g., the pressure at which a high pressure switch restricts operation of at least a portion of the air conditioning system to inhibit mechanical failure of the system). The predetermined maximum pressure may be selected such that operation of the high pressure switch may be avoided when using the bypass line.

In some implementations, in an air conditioner that includes a microchannel condenser, as the ambient temperature becomes elevated (e.g., ambient temperatures greater than 125 degrees Fahrenheit and/or 116 degrees Fahrenheit), the pressure in the microchannel condenser increases (e.g., due to the capacity differences between the evaporator and the microchannel condenser). A sensor can be disposed proximate at least a portion of the condenser and may measure the pressure (e.g., pressure reading). As the pressure (e.g., inlet, outlet, differential, and/or average) of the microchannel increases, the likelihood of mechanical failure increases, and so a high pressure switch may operate at a predetermined activation pressure (e.g., a maximum operational pressure) to inhibit mechanical failure of the air conditioner. For example, the high pressure switch may restrict operation of one or more components of the air conditioner (e.g., compressor) and/or open a vent. The predetermined maximum pressure may be determined based on the high pressure switch activation pressure, in some implementations. For example, the predetermined maximum pressure may be a predetermined amount less than the maximum operational pressure (e.g., the predetermined maximum pressure may be approximately 15 to approximately 20 psi less than the predetermined maximum operational pressure). The measured pressure may be compared to the predetermined maximum pressure to determine whether to allow a part of the refrigerant to be diverted to the bypass line. When the measured pressure exceeds the predetermined maximum pressure, a valve coupled to the sensor may open and allow refrigerant to flow through the bypass line. The bypass may reduce the pressure and/or inhibit pressures in the microchannel condenser from elevating to the activation pressure. When the measured pressure does not exceed the predetermined maximum pressure, fluid flow through the bypass line may be restricted (e.g., by the valve coupled to the sensor). For example, the bypass line may be utilized to reduce the pressure, when needed to control pressure in the microchannel condenser and/or to inhibit mechanical failure. When the pressure of the microchannel condenser is within operational parameters (e.g., less than the predetermined maximum pressure and/or predetermined maximum operational pressure), the fluid flow through the bypass line may be restricted to increase efficiency of the system and/or control of pressure within the evaporator.

Although various implementations have been described in terms of pressure and pressure sensors, other properties may be utilized in the various systems and/or processes. For example, a temperature sensor may be utilized. Temperatures, such as ambient temperature may be measured by sensors and the valve in the bypass line may operate based on the measured temperature. Although a valve coupled to the bypass line that opens to allow fluid flow through the bypass line has been described, other valve configurations may be allowed as appropriate. For example, a three way valve coupled to the junction between the bypass line and the high pressure portion and/or low pressure portion, may direct fluid flow.

In some implementations, ambient temperature may include a temperature proximate the high pressure portion, a temperature proximate the condenser, and/or a temperature proximate a condenser fan. For example, ambient temperature may include a measure of the temperature of the air proximate an outdoor portion (e.g., a condenser) of an air conditioning system. As another example, ambient temperature may include a measure of the temperature of a fluid removing heat from the refrigerant in the condenser. Temperature measurements may cause an adjustment to the maximum allowed pressure, depending on the properties of the refrigerant used, or other factors.

In some implementations, a pressure across a line coupling components may be substantially constant. For example, a pressure drop across a line coupling components may be less than approximately 5 percent. As an example, a pressure proximate an inlet of a high pressure portion and/or condenser may be substantially equal to the pressure proximate an outlet of a compressor. A sensor measuring a pressure in a line may not substantially affect the pressure. In some implementations, a pressure across the high pressure portion and/or the pressure across the low pressure portion may be substantially constant. For example, a pressure drop across the high pressure portion may be less than approximately 5 percent. The pressure drop across the low pressure portion may be less than approximately 5 percent.

Although an orifice has been described, any appropriate metering device may be utilized to control fluid flow into the evaporator. For example, a thermal expansion valve may be utilized.

Although an operation of the cycle is described where cool air is provided to a location by the evaporator which is the indoor coils, the cycle may be reversed such that hot air is provided to a location by the indoor coils. For example, heat may transfer from refrigerant in the indoor coils to the air from the indoor blower.

In some implementations, the air conditioning system may include a controller. The control device for the bypass valve may be a portion of the controller and/or separate from the controller. A controller may be coupled to various components of the air conditioning system. For example, the controller may be communicably coupled to an evaporator, an evaporator blower, a compressor, a condenser, a condenser fan, bypass line, sensor, high pressure switch, control device of the sensor, valve, and/or thermal expansion valve. The controller may be a computer or other programmable logic device. The controller may include a processor that executes instructions and manipulates data to perform operations of the controller and a memory. The processor may include a programmable logic device, a microprocessor, or any other appropriate device for manipulating information in a logical manner and memory may include any appropriate form(s) of volatile and/or nonvolatile memory, such as a repository. A memory may include data, such as predetermined maximum operating properties (e.g., temperatures and/or pressures), activation pressures, predetermined maximum properties (e.g., temperatures and/or pressures), periods of time that operations should run, and/or any other data useful to the operation of the air conditioner. In addition, various types of software may be stored on the memory. For example, instructions (e.g., operating systems and/or other types of software), an operation module, a bypass operation module, and/or a high pressure switch module may be stored on the memory. The operation module may operate the air conditioner during normal operations (e.g., operations based at least partially on requests for operation from a user, operations in which flow though the bypass is restricted). The bypass operation module may measure and/or monitor properties of the air conditioning system, retrieve data (e.g., predetermined operational maximums and/or predetermined maximum values), compare data to monitored properties, determine whether to open and/or close a bypass line, etc. A high pressure switch module may measure and/or monitor properties, such as pressure, retrieve data (e.g., predetermined operational maximum), compare monitored properties to retrieved data, and/or determine an appropriate action based on the retrieved data (e.g., restrict operation of one or more components of the air conditioner and/or allow normal operations).

A communication interface may allow the controller to communicate with components of the air conditioner, other repositories, and/or other computer systems. The communication interface may transmit data from the controller and/or receive data from other components, other repositories, and/or other computer systems via network protocols (e.g., TCP/IP, Bluetooth, and/or Wi-Fi) and/or a bus (e.g., serial, parallel, USB, and/or FireWire).

The controller may include a presentation interface to present data to a user. For example, to provide for interaction with a user, the systems and techniques described here can be implemented on a computer having a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user and a keyboard and a pointing device (e.g., a mouse or a track pad) by which the user can provide input to the computer. Other kinds of devices can be used to provide for interaction with a user as well; for example, feedback provided to the user by an output device can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form, including acoustic, speech, or tactile input. The controller may include clients and servers. A client and server are generally remote from each other and typically interact through a communication network. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other. A client may allow a user to access the controller and/or instructions stored on the controller. The client may be a computer system such as a personal computer, a laptop, a personal digital assistant, a smart phone, or any computer system appropriate for communicating with the controller. These computer programs (also known as programs, software, software applications or code) include machine instructions for a programmable processor, and can be implemented in a high-level procedural and/or object-oriented programming language, and/or in assembly/machine language. As used herein, the term “machine-readable medium” refers to any computer program product, apparatus and/or device (e.g., magnetic discs, optical disks, memory, Programmable Logic Devices (PLDs)) used to provide machine instructions and/or data to a programmable processor, including a machine-readable medium that receives machine instructions as a machine-readable signal. The term “machine-readable signal” refers to any signal used to provide machine instructions and/or data to a programmable processor.

Although users have been described as a human, a user may be a person, a group of people, a person or persons interacting with one or more computers, and/or a computer system. Various implementations of the systems and techniques described here can be realized in digital electronic circuitry, integrated circuitry, specially designed ASICs (application specific integrated circuits), computer hardware, firmware, software, and/or combinations thereof. These various implementations can include implementation in one or more computer programs that are executable and/or interpretable on a programmable system including at least one programmable processor, which may be special or general purpose, coupled to receive data and instructions from, and to transmit data and instructions to a storage system (e.g., repository), at least one input device, and at least one output device.

Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps. 

What is claimed is:
 1. An HVAC system comprising an evaporator, condenser, pressure sensor, and compressor, the system comprising: a bypass line, the bypass line operable to direct at least some refrigerant away from the condenser inlet and toward the evaporator inlet; and a controller communicatively coupled to the pressure sensor and the bypass line, the controller operable to open the bypass line when the pressure within the liquid line reaches a set value; wherein the bypass line comprises an orifice, the orifice operable to relieve pressure within the HVAC system.
 2. The HVAC system of claim 1 wherein the condenser comprises a microchannel condenser.
 3. The HVAC system of claim 1 wherein the controller opens the bypass line by opening a solenoid valve.
 4. The HVAC system of claim 1 wherein the bypass line comprises a pressure regulating valve.
 5. The HVAC system of claim 1 further comprising a second pressure sensor.
 6. The HVAC system of claim 1 further comprising a distributor.
 7. The HVAC system of claim 1 wherein the pressure sensor is located proximate the discharge line of the compressor.
 8. The HVAC system of claim 1 wherein the bypass line comprises an expansion device and a solenoid valve.
 9. A method of operating an HVAC system comprising: receiving, at a controller, a signal to start the HVAC system; starting, by the controller, the HVAC system; receiving, at the controller, a pressure measurement within the HVAC system; sending, by the controller, a message to open a valve in a bypass line when the pressure measurement is above a set value, thereby directing at least some refrigerant away from a condenser inlet and toward an evaporator inlet, wherein the bypass line comprises an orifice; and sending, by the controller, a message to close the valve when a predetermined event has occurred.
 10. The method of claim 9 wherein the HVAC system comprises a microchannel condenser.
 11. The method of claim 9 wherein the predetermined event is a period of time.
 12. The method of claim 9 wherein the predetermined event occurs when the pressure within the HVAC system drops below the set value.
 13. The method of claim 9 wherein the valve is a solenoid valve.
 14. The method of claim 9 wherein the bypass line comprises an expansion device and a solenoid valve.
 15. The method of claim 9 wherein in the pressure measurement is received from a pressure sensor proximate the discharge line of the compressor.
 16. The method of claim 9 wherein HVAC system comprises a distributor.
 17. A method of relieving pressure within an HVAC system comprising: starting the HVAC system; receiving a pressure notification when pressure within the HVAC system exceeds a set value; opening a bypass line in response to the pressure notification, the bypass line capable of diverting at least some refrigerant away from a condenser inlet and toward an evaporator inlet, the bypass line comprising a valve and an orifice; and closing the bypass line when a predetermined event has occurred.
 18. The method of claim 17 wherein the HVAC system comprises a microchannel condenser.
 19. The method of claim 17 wherein the HVAC system comprises a fin tube evaporator.
 20. The method of claim 17 wherein the predetermined event is a period of time. 